CN103442880A - Process for producing solar cell sealing sheet - Google Patents

Abstract

The present invention relates to a method for producing a solar cell sealing sheet. The production method sequentially performs the following steps: Step (a): forming a resin composition melted by heating into a sheet, followed by cooling to obtain a process sheet Step (b): heating at least one surface of the process sheet obtained in the above step (a) for 22 to 55 seconds, and during the heating, the temperature of the surface is made to be equal to or higher than the melting point of the resin composition constituting the surface portion Temperature step; step (c): a step of setting the temperature of the surface of the sheet heated in the step (b) to a specific range, and then pressing an embossing roller against the surface to form an embossed shape on the surface. According to the present invention, a solar cell sealing sheet having a small heat shrinkage and having a clear embossed shape can be efficiently produced at low cost.

Description

Manufacturing method of solar cell sealing sheet

technical field

The present invention relates to a method for manufacturing a solar cell sealing sheet. In particular, it is related with the manufacturing method of the sheet|seat suitable for manufacturing the solar cell encapsulating sheet which heat shrinkage|shrinkage is small, and a clear protrusion was formed in the surface.

Background technique

In recent years, solar cells that directly convert sunlight into electrical energy have attracted attention from the viewpoints of efficient use of resources, prevention of environmental pollution, and the like, and various developments have been made. A solar cell is generally configured by sealing the solar cell with a solar cell sealing sheet (hereinafter referred to as sealing sheet) between a light-receiving surface protection material represented by a glass substrate and a back surface protection material called a back sheet.

As a solar cell module, a mainstream crystalline silicon type solar cell is generally manufactured as follows. First, a glass substrate, a sealing sheet, a solar cell (silicon power generation element), a sealing sheet, and a back sheet are laminated in this order. The sealing sheet is generally composed of ethylene-vinyl acetate copolymer (hereinafter referred to as EVA). Next, this laminated body is heated in vacuum by vacuum lamination, and the sealing sheet is heat-melted and cross-linked and solidified. In this way, a solar cell module in which each constituent member was bonded without air bubbles was manufactured.

In the manufacture of such a solar cell module, if the shrinkage of the sealing sheet during heating is large, the silicon power generating element may be damaged or the position of the cell may be shifted due to the shrinkage deformation. Therefore, the sealing sheet is required to be small in shrinkage when heated. In addition, in recent years, in order to effectively utilize the resources of crystalline silicon and reduce the cost for popularizing solar cell modules, the thickness of silicon power generation elements has been reduced to about 100 μm, which in turn has become easy to break. Therefore, the demand for reducing the heat shrinkage of the sealing sheet is further increased. Therefore, various methods of reducing the heat shrinkage rate of the sealing sheet have been studied. (eg, Patent Document 1).

Furthermore, in addition to the above-mentioned requirements for manufacturing, the reliability of solar cell modules is extremely important in order to use them for a long period of time after manufacture. Typical failures occurring in solar cell modules used for a long period of time include peeling between solar cells and sealing sheets, and appearance defects such as swelling, and a reduction in power generation associated therewith. The reasons for these adverse phenomena are not necessarily clear, but they have been studied from the perspective of the raw materials constituting the sealing sheet. For example, a method of adjusting the viscosity of EVA constituting the sealing sheet (Patent Document 2), a method of adding a silane coupling agent in order to improve the adhesive strength between the solar cell and the sealing sheet (Patent Document 3), and the like have been studied.

In addition, various studies have been conducted from the structural aspects of sealing sheets. In order to prevent expansion and the like associated with long-term use, it is important to bond the constituent members inside the module immediately after manufacture with as little air bubbles as possible. Therefore, attempts have been made to form various protrusions and depressions such as embossed shapes on the surface of the sealing sheet for the purpose of facilitating air leakage during vacuum lamination. In addition, these protrusions and depressions are sometimes formed for the purpose of preventing damage to the solar cell due to pressing pressure at the time of lamination, improving handleability of the sealing sheet, and the like. Regarding the embossed pattern, detailed proposals have been made regarding its shape, depth, and the like (Patent Documents 4 and 5).

As mentioned above, when manufacturing a sealing sheet, it becomes important to form a clear embossed shape on the surface of a sealing sheet, reducing heat shrinkage of a sealing sheet. As a method proposed so far, when casting a sheet extruded from a T-die using an extruder such as a twin-screw extruder, it is disclosed that an embossed shape is formed on the sheet immediately below the die, and then heat shrinkage is reduced as necessary. The method of annealing treatment (Patent Document 6).

prior art literature

patent documents

Patent Document 1: Japanese Patent Laid-Open No. 2000-084996

Patent Document 2: Japanese Patent Laid-Open No. 2002-170971

Patent Document 3: Japanese Patent Laid-Open No. 2000-183382

Patent Document 4: Japanese Patent Laid-Open No. 2006-134970

Patent Document 5: Japanese Patent Laid-Open No. 2002-185027

Patent Document 6: Japanese Patent Laid-Open No. 2010-100032

Contents of the invention

The problem to be solved by the invention

In the production method of Patent Document 6, after forming an embossed shape on the surface of a sheet in the manufacturing process (hereinafter referred to as a process sheet), the process sheet is annealed. Therefore, if the process sheet is sufficiently heated in order to reduce the heat shrinkage of the sealing sheet, the embossed shape formed on the surface of the process sheet will collapse by this heating. Conversely, if the heating of the process sheet is moderated in order to maintain the embossed shape, the annealing treatment becomes insufficient. Thus, in the manufacturing method of patent document 6, it is very difficult to simultaneously reduce heat shrinkage and form embossed shape clearly.

In addition, as a method of reducing the heat shrinkage of the sealing sheet, generally, as disclosed in Patent Document 1, when the resin film is conveyed by a conveyor having a plurality of rollers, the roll of the entrance side is used to The peripheral speed is faster than the peripheral speed of the roller on the exit side, etc., and shrinks the process sheet to reduce heat shrinkage. However, in this method, since the sheet is stretched during the annealing treatment, heat shrinkage is not sufficiently removed, and it is necessary to perform annealing treatment for a long time of 1 to 2 minutes.

In addition, since the sealing sheet made of EVA often contains a crosslinking agent, the molding temperature of the process sheet becomes low, so a large amount of residual strain remains on the process sheet. Furthermore, the residual strain tends to be non-uniform in the width direction of a wide process sheet. When the process sheet in such a state is annealed as described above, the planarity of the sheet is impaired, the thickness becomes non-uniform, and the process sheet bends during the annealing process. In addition, it is very difficult to sandwich and press the process sheet in such a state with a plurality of rollers, and to continuously perform embossing and the like.

Therefore, an object of the present invention is to provide a manufacturing method capable of forming a clear embossed shape on the surface of the sealing sheet while sufficiently reducing heat shrinkage of the sealing sheet.

method used to solve the problem

In order to solve the said subject, the manufacturing method of the solar cell sealing sheet of this invention performs following process (a), process (b), and process (c) sequentially, It is characterized by the above-mentioned.

Step (a): A step of molding the resin composition melted by heating into a sheet, followed by cooling to obtain a sheet

Step (b): heating at least one surface of the process sheet obtained in the above step (a) for 22 to 55 seconds, and during the heating, the temperature of the surface is brought to a temperature equal to or higher than the melting point of the resin composition constituting the surface portion

Step (c): The temperature of the surface of the step sheet heated in the above step (b) is (melting point of the resin composition constituting the surface portion - 10° C.) to (the temperature of the resin composition constituting the surface portion Melting point + 20°C), and then pressing the embossing roller against the surface to form an embossed shape on the surface

The effect of the invention

According to the present invention, a solar cell sealing sheet having a small heat shrinkage and having a clear embossed shape can be produced efficiently and at low cost.

Description of drawings

FIG. 1 is a schematic schematic diagram showing an example of the method for producing the solar cell sealing sheet of the present invention.

FIG. 2 is a schematic schematic diagram showing an example of a conventional method for producing a solar cell sealing sheet.

It is a figure explaining the method of measuring the height of the protrusion of the solar cell sealing sheet which formed the protrusion on one surface.

It is a figure explaining the method of measuring the height of the protrusion of the solar cell sealing sheet which formed the protrusion on both surfaces.

FIG. 5 is a diagram showing the length D of the base of the protrusion.

Detailed ways

[Manufacturing method of solar cell sealing sheet]

The manufacturing method of the solar cell sealing sheet of this invention performs following process (a), process (b), and process (c) sequentially.

Step (a): A step of molding the resin composition melted by heating into a sheet shape, and then cooling to obtain a step sheet.

Step (b): heating at least one surface of the process sheet obtained in the above step (a) for 22 to 55 seconds, and during the heating, the temperature of the surface is brought to a temperature equal to or higher than the melting point of the resin composition constituting the surface portion .

Step (c): The temperature of the surface of the step sheet heated in the above step (b) is (melting point of the resin composition constituting the surface portion - 10° C.) to (the temperature of the resin composition constituting the surface portion Melting point + 20°C), followed by pressing an embossing roller against the surface to form an embossed shape on the surface.

Hereinafter, the manufacturing method of the solar cell sealing sheet of this invention is demonstrated with reference to drawings. FIG. 1 is a schematic diagram showing an embodiment of one of the production methods of the present invention.

[Process (a): film forming process]

First, the step (a) will be described. The step (a) is a step of molding the raw material resin into a sheet and cooling it to obtain a process sheet. Hereinafter, the step (a) is referred to as a film forming step.

In the film forming process in Fig. 1, an extruder 11 is installed to melt and knead the raw material resin and additives at a high temperature, a gear pump 31 to reduce the pressure change of the resin to stabilize the thickness of the sheet, and the kneaded The die head 12 extruding the melted resin into a sheet, and the polishing rollers 13a, 13b, and 13c for cooling and solidifying the extruded high-temperature process sheet into a solid process sheet.

As the extruder 11, a single-screw extruder and a twin-screw extruder can be used. When using a twin-screw extruder, it is preferable from the viewpoints of productivity, kneadability of resin and additives, and the like. In the case of using a single-screw extruder, since the inside of the extruder is filled with resin, the pressure change in the die portion at the front end of the extruder is relatively small, so it is not necessary to install a quantitative supply device such as a gear pump 31 . In the case of using a twin-screw extruder, since the inside of the extruder is not in a full state, it is preferable to install a quantitative supply device such as a gear pump 31 between the extruder and the die.

The raw material resin and additives charged into the extruder 11 may be charged into a mixture previously mixed with a mixer, a stirrer, or the like, or may be charged separately. In addition, a method of side-feeding the additive from the middle of the extruder, or adding it with an injection pump or the like in the case of a liquid additive, or the like may be used.

The temperature at the time of kneading the raw resin and the additive depends on the type and viscosity of the resin used, but is preferably in the range of (melting point of raw resin + 10°C) to (melting point of raw resin + 60°C). In addition, in the present invention, the melting point is the endothermic peak temperature when the temperature is raised at 10° C./min in differential scanning calorimetry (DSC). In the case of an EVA sheet generally used as a sealing sheet, an organic peroxide is often contained as an additive in order to crosslink the EVA. Therefore, it is necessary to perform kneading while paying attention not to decompose the organic peroxide as much as possible. Therefore, as the resin temperature, for example, in the case of EVA having a melting point of about 70°C, kneading is preferably carried out in the range of 80 to 130°C. More preferably, it is the range of 100-120 degreeC. If it is less than 80°C, the kneadability becomes insufficient, and the uniform dispersibility of additives may decrease. As a result, the appearance of the sealing sheet may deteriorate. When it exceeds 130 degreeC, when an organic peroxide is mix|blended, an organic peroxide will decompose, the quality of a sealing sheet may become unstable, and continuous productivity may also fall.

In addition, in the process of FIG. 1, an extruder is provided as the method of film-forming process sheet|seat, However, Well-known different methods, such as molding by calender roll, can also be used.

The molten resin obtained by melting and kneading the raw material resin and additives with the extruder 11 or the like is extruded into a sheet form using the die 12 . As the die 12, a T-type die, a circular die, or the like can be used. Since the flat die has a wide shape according to the width of the sheet to be extruded, it will be T-shaped when installed in an extruder, so it is collectively called a T-shaped die. In addition, since the T-die has different residence time and flow rate in the width direction of the die, problems such as thickness variation and uneven thickness in the width direction when heating the process sheet in step (b) are prone to occur. In order to solve these problems, it is also preferable to use a cylindrical circular die. A circular die is a cylindrical die for extruding a resin into a cylindrical shape and cutting it to form a sheet, and the physical properties in the width direction of the sheet tend to be relatively uniform.

In addition, in the case of using a T-die, multiple extruders can be used to extrude different resin compositions, and the process sheet can be laminated by a co-extrusion method such as a feed block method or a multi-die method. constitute. By forming such a laminated structure, the necessary functions of each layer can be separated as a sealing sheet, and the cost can be reduced by adjusting the amount of additives.

The process sheet extruded using the die head 12 is molded into a sheet shape by polishing rolls 13a, 13b, and 13c. The buff roll is a process sheet conveying device composed of a plurality of rollers for simultaneously pressing the molten resin between a pair of rollers to shape the thickness and surface properties of the sheet. Each roller constituted has a mechanism for adjusting the temperature suitable for cooling and shaping of the molten resin, and a mechanism for adjusting the gap between the rollers and the pressing pressure. In addition, if necessary, it is preferable to prevent the sticking of the process sheet and improve the moldability by passing temperature-adjusted water such as cooling water. It is preferable to adjust the temperature of cooling water to the range of 0-30 degreeC. Among the polishing rollers, the most upstream polishing roller 13 a may be easily adhered to the surface of the roller depending on the composition of the resin used. Therefore, it is preferable to wrap silicone rubber or the like on the surface to improve the release property. In addition, in order to improve conveyance, it is also preferable that the facing roller 13b of the buff roller 13a positioned on the most upstream side is a metal roller having a matte surface form. Regarding the surface roughness of a sandy surface, the 10-point average roughness Rz defined in JIS B0601-1994 is preferably in the range of about 2 to 10 μm. When the surface of the polishing roller 13a is wound with silicone rubber or the like, and the facing roller 13b is a metal roller having a sandy surface, the thickness of the silicone rubber on the surface of the polishing roller 13a is preferably 3 to 10mm. More preferably, it is 4-8 mm. If the thickness of the silicone rubber is less than 3 mm, the transfer of the matte pattern becomes insufficient, and the process sheet may adhere to a free roller or the like for conveying the process sheet. If the thickness of the silicone rubber exceeds 10 mm, the heat from the molten resin accumulates on the surface of the rubber, so that the resin may adhere to the roller.

[Step (b): Annealing treatment step]

Next, the step (b) will be described. The purpose of the step (b) is to remove the residual strain of the process sheet molded in the film forming step and reduce the heat shrinkage of the process sheet. For the step (b), a method of passing a process sheet over a plurality of transport rollers 17 while being heated by the heater 16 installed in the annealing furnace 15 is exemplified. Hereinafter, the step (b) is referred to as an annealing step.

The heater 16 used to heat the process sheet is not particularly limited as long as it can heat the process sheet, and known methods such as ceramic heaters, stainless steel heaters, and sheath heaters can be used. In particular, the method of heating the sheet by infrared rays is preferable since it can be heated uniformly in the thickness direction of the sheet. In addition, heating with a heating medium such as hot air and steam, a method of contacting a heated roll, and the like can also be preferably used. These heating methods may be used alone or in combination of some methods.

The conveying roller 17 used for conveying the process sheet preferably has excellent mold releasability in order to convey the heated process sheet. Therefore, it is possible to use polytetrafluoroethylene, perfluoroethylene propylene copolymer, perfluoroalkoxy chain coated with polytetrafluoroethylene, perfluoroethylene propylene copolymer, perfluoroalkoxy chain, etc. Rolls of fluororesin such as alkanes. Alternatively, a roll obtained by winding paper, a film, or the like that has been coated with release properties on the surface of a metal roll may be used. The means for imparting these releasability is not particularly limited, and conventionally known methods can be used. As the degree of releasability of these rollers, it is preferable to use a material having a peeling strength of 5 N/mm or less with respect to cellophane tape manufactured by Nichiban Co., Ltd. according to the method specified in JIS Z0237-2009. In addition, it is preferable that the speed of the conveyance roller 17 in the furnace can be controlled individually according to the shrinkage of the process sheet, since heat shrinkage can be efficiently removed.

The heater 16 and the transport roller 17 are preferably installed in the annealing furnace 15 so that the temperature in the furnace is stabilized and the heat treatment of the process sheet is stabilized while minimizing the contact with the outside air. In addition, for the purpose of uniformly stabilizing the temperature in the furnace, it is one of the preferable aspects to supply hot air into the furnace.

In addition, it is preferable to install a pair of rolls 14 upstream of the annealing furnace 15 as needed. By providing the roll 14, it is possible to block the influence of the annealing process on the film forming process, which is preferable. Specifically, it is possible to prevent the shrinkage of the process sheet from being affected by the film forming process, and to stabilize the supply of the process sheet in the annealing process.

In addition, it is preferable that the sheet take-out roll 18 is provided in advance between the exit of the annealing furnace 15 and the embossing roll 20 . The sheet take-out roller 18 plays a role of taking out the process sheet from the annealing furnace 15 . If there is no sheet take-out roll 18, the sheet may be stretched and deformed in the process between the roll 17 closest to the exit side and the embossing roll 20 in the annealing furnace. In addition, during the annealing process, heat shrinkage of the process sheet may cause unevenness and wrinkles in the width direction of the process sheet. Therefore, in order to remove the wrinkles, the sheet take-out roll 18 is also preferably a tenter roll (bending roll). In addition, it is preferable that the sheet take-out roller 18 is preliminarily provided with mold releasability similarly to the conveyance roller 17 in the furnace.

In addition, if the surface temperature of the sheet take-out roller 18 is too low, the sheet in the process of feeding to the embossing roller may be cooled, and the transferability of the embossed shape may decrease. Conversely, if the surface temperature is too high, the process sheet may adhere to the sheet take-out roller 18, making it difficult to convey the process sheet. Therefore, the surface temperature of the sheet take-out roller 18 is preferably adjusted in advance to a temperature in the range of 20 to 80°C. More preferably, the surface temperature is equal to or lower than the temperature of the process sheet at the exit of the annealing furnace. If the surface temperature of the sheet take-out roll 18 is higher than the surface temperature of the process sheet coming out of the annealing furnace, the process sheet may stick to the roll.

In order to prevent the temperature drop of the process sheet, the distance between the annealing furnace 15 and the embossing roll 20 is preferably as short as possible. Therefore, a plurality of sheet take-out rollers 18 may be provided, but less is preferable, preferably at most three or less, and more preferably one or two.

When performing the annealing step and the subsequent step (c) continuously, it is preferable to control the surface temperature of the process sheet exiting the annealing furnace 15 and the surface temperature of the process sheet introduced into the embossing roll in the step (c). Therefore, in order to accurately grasp the surface temperature of the process sheet and measure the surface temperature of the exit portion of the annealing furnace 15 and the surface temperature of the process sheet immediately before embossing, it is preferable to provide a non-contact infrared thermometer 33 . In addition, it is preferable to install a plurality of non-contact thermometers also in the annealing furnace 15 to measure the surface temperature of the process sheet.

In the annealing treatment step, heating is performed until the maximum temperature of at least one surface of the process sheet becomes a temperature equal to or higher than the melting point of the resin composition constituting the surface portion. The surface on the heated side is embossed in the next step (c). Here, the "resin composition constituting the surface part" refers to the resin composition constituting the process sheet when the process sheet is a single-layer sheet, and when the process sheet is a laminated sheet in which a plurality of layers are laminated. The bottom is the resin composition constituting the layer of the heated side surface. Even if an annealing treatment is performed such that the maximum temperature is only lower than the melting point of the resin composition, the effect of reducing the heat shrinkage rate is insufficient, or long-term treatment is required. In addition, the maximum temperature of the surface is preferably in the temperature range of (melting point of the resin composition constituting the heated surface portion + 5° C.) to (melting point of the resin composition constituting the heated surface portion + 35° C.) Inside. If the temperature in the annealing treatment is too high, the process sheet may adhere to the conveyance roll, or the planarity may be lowered, or wrinkles may be generated in the next step (c) due to this. For example, in the case of a process sheet made of EVA resin having a melting point of 71°C, the maximum temperature attained on the surface in the annealing process is preferably in the range of 76 to 106°C.

The time for heating the process sheet, that is, the time for the process sheet to stay in the annealing furnace is within the range of 22 to 55 seconds. The heating time is the time required for the surface temperature of the process sheet cooled by the polishing roller 13 to reach the melting point or higher and the time for performing annealing treatment for reducing heat shrinkage after reaching the melting point temperature or higher. total. If the heating time is less than 22 seconds, heat shrinkage will be insufficiently removed. Even if the heating time exceeds 55 seconds, the effect is saturated, and only the length of the annealing furnace becomes ineffectively long. The lower limit of the heating time is preferably 22 seconds or more, more preferably 25 seconds or more. The upper limit of the heating time may be as long as heat shrinkage can be sufficiently removed, and it is preferably short, preferably 45 seconds or less, more preferably 40 seconds or less.

[Process (c): Embossing Process]

Next, the process (c) is demonstrated. The step (c) is a step of embossing the process sheet brought into a high-temperature state by heating in the annealing step to form an embossed shape on the surface of the process sheet. In the process (c), the embossing roll 20, the embossing counter roll 19, and the cooling roll 21 for forming an embossed shape on the process sheet are provided. Hereafter, this process (c) is called an embossing process.

On the surface of the embossing roller 20 , engravings corresponding to the embossing shape to be formed on the process sheet are given in which the embossing shape is reversed. The embossed shape formed on the process sheet may be a random shape, a geometric pattern, etc., and may be determined as necessary. However, if the formation of the embossed shape is insufficient, the conveyability of the process sheet and the sticking when rolled into a roll are likely to occur, or the leakage of air is difficult when it is made into a solar cell module, which may cause air bubbles to be generated in the module. . The engraved pattern on the surface of the embossing roller may be in the shape of a hemispherical cone, a triangular pyramid, a quadrangular pyramid, a hexagonal pyramid, or a cone, and a trapezoid whose tops are flattened. Also, these shapes may be mixed patterns. Among them, hemispherical shape and/or quadrangular pyramid shape are preferable. Here, "hemispherical and quadrangular pyramidal shapes" refer to engravings in which hemispherical and quadrangular pyramidal shapes are mixed. The hemispherical shape is preferable from the viewpoint of being less likely to receive a concentrated load when the sealing sheet is pressed against the solar battery cell and can evenly distribute the load. Moreover, since unevenness of the reflected light of a sealing sheet does not generate|occur|produce easily, and surface quality is excellent, it is preferable that it is a quadrangular pyramid shape. In addition, in order to express the characteristics of both the hemispherical shape and the quadrangular pyramid shape, it is also preferable that the patterns of the hemispherical shape and the quadrangular pyramid shape are mixed. In the case where the hemispherical shape and the quadrangular pyramid shape are mixed, the respective ratios may be arbitrarily determined according to which characteristic is more required. Particularly preferred are all hemispherical patterns.

When the engraving on the surface of the embossing roller is too deep, a large pressing pressure is required during the embossing process, and the facility becomes large. Therefore, although the depth of the engraving of the embossing roll is related to the thickness of the process sheet, it is preferably in the range of 65 to 350 μm. In addition, the depth of the engraving of the embossing roll means the distance from the center of the embossing roll to the surface of the embossing roll (a portion not engraved) and the distance from the center of the embossing roll to the engraved concave (valley portion). The difference in the distance of the deepest part. The depth of the engraving is represented by the maximum height Pz (μm) measured using a surface roughness measuring machine in accordance with JISB0601 (2001).

It is preferable to further provide depressions with a depth of 1 to 20 μm on the surface of the embossing roll. By performing embossing using an embossing roll provided with such minute depressions, minute protrusions can be formed on the surface of the sheet. As a result, the slidability of the sheet is improved to facilitate handling, and the fine protrusions scatter light to improve the whiteness of the sheet, thereby facilitating the inspection of attached foreign matter and the like. Such minute depressions can be easily formed by engraving the surface of the embossing roll and then performing known sandblasting or the like. The depth of minute depressions can be adjusted according to the particle size and pressure conditions during blasting.

The embossing counter roll 19 facing the embossing roll is preferably a metal roll wrapped with rubber in order to improve the transferability of the engraving on the surface of the embossing roll to the process sheet. The type of rubber is silicone rubber, nitrile rubber, neoprene, etc., and is not particularly limited, but is preferably rubber having a type A hardness in the range of 65° to 85° according to JIS K6253-2006. If it is less than 65° and exceeds 85°, the transferability of the embossed shape may decrease. Of these rubbers, silicone rubber is most preferable because of its good releasability with process sheets that tend to stick at high temperatures.

In the embossing process, the temperature of the surface heated by the annealing process of the process sheet supplied to the embossing roll is (the melting point of the resin composition constituting the surface - 10° C.) to (the resin composition constituting the surface within the temperature range of the melting point of the substance + 20°C). If it is less than (melting point of the resin composition-10 degreeC), the transferability of an embossed shape will fall. If it exceeds (the melting point of the resin composition+20° C.), the temperature of the process sheet in the annealing process will be too high, and wrinkles and the like will easily occur in the annealing process. For example, when the layer on the surface side is made of EVA resin having a melting point of 71°C, the surface temperature during embossing is within the range of 61°C to 91°C.

In addition, as for the pressing pressure of the embossing roller 20, the linear pressure received by the process sheet is preferably in the range of 150 to 500 N/cm. More preferably, it is the range of 200-450 N/cm. If the linear pressure is less than 150 N/cm, the transferability of the embossed shape may decrease. If a linear pressure exceeding 500 N/cm is to be added, the facility needs to be enlarged, and in this case, the life of the opposed rubber rollers will be shortened.

In the prior art shown in Fig. 2, although the pressing pressure of the embossing roller 13b' is high, a linear pressure of about 100 N/cm is sufficient. This is presumed to be because the temperature of the resin extruded from the T-die is, for example, in the case of using EVA resin with a melting point of 71° C., which is often in the range of 100 to 120° C. For shape transfer, a linear pressure of about 100N/cm is sufficient. On the other hand, in the manufacturing method of this invention, embossing is performed in the temperature range of (melting point of a resin composition-10 degreeC) - (melting point of a resin composition+20 degreeC) as mentioned above. As described above, if the surface temperature of the process sheet during embossing becomes low, the embossed shape will not be easily transferred, so it is preferable to increase the pressing pressure required for embossing. That is, the linear pressure is preferably 150 N/cm or more. In addition, the linear pressure referred to in the present invention is a value obtained by dividing the pressing load of the roller by the surface length of the roller.

In addition, in such embossing at a relatively low temperature, it is preferable to wrap the process sheet around the embossing roller 20 in order to improve the transferability of the embossed shape. Specifically, it is preferable that the angle of attachment to the embossing roll is in the range of 30 to 270°. If only shallow embossing is provided, the wrapping angle may be less than 30°. In order to give deep and clear embossing, the wrapping angle is preferably 30° or more. In addition, the hug angle can be easily calculated from the ratio of the length of the arc of the portion of the embossing roller 20 that contacts the process sheet 32 to the circumference of the embossing roller. For example, when the wrapping angle is 90°, it means that the process sheet is in contact with the process sheet at a portion corresponding to a length of 1/4 of the circumference of the embossing roll.

The surface temperature of the embossing roll 20 in the embossing step is preferably not higher than (the melting point of the resin composition constituting the surface portion on which the embossed shape is transferred - 20° C.). When the temperature of the embossing roll is low, the releasability of the process sheet becomes better, and the process sheet is less likely to be wound around the roll. As a result, the load at the time of peeling the process sheet from the embossing roll is reduced, and a solar cell sealing sheet of higher quality can be obtained.

After the process sheet is released from the embossing roll, the process sheet is cooled by the cooling roll 21 to quickly lower the surface temperature of the process sheet to around room temperature.

With regard to the process sheet 32 formed in an embossed shape by removing heat shrinkage by such film forming and annealing treatment, after inspecting for defects and adjusting the size of the process sheet to a desired width, it is wound up by a winding machine or the like. Rolls, or slices cut into desired lengths, are used in the manufacture of solar cell modules.

[Solar cell sealing sheet]

Next, the solar cell sealing sheet will be described. The sealing sheet preferably has independent protrusions on the surface with a height of 60 to 300 μm. By having independent protrusions with a height of 60 μm or more on the surface of the sealing sheet, air remaining between the sealing sheet and the solar cell can be efficiently removed from multiple directions during vacuum lamination during solar cell module manufacturing. To remove, suppress the occurrence of air bubbles. In addition, the pressing force of the sealing sheet against the solar cell can be dispersed, and the occurrence of cell cracking can be suppressed. If the shape of the surface of the sealing sheet is not an independent protrusion but a continuous groove shape, the degassing in the direction perpendicular to the groove becomes insufficient, and the remaining air becomes air bubbles. In addition, when the height of the protrusions is 300 μm or less, the concentration of the load on the top of the protrusions during vacuum lamination is suppressed, and the solar cell can be prevented from being broken. Here, the "independent protrusion" refers to a protrusion whose base length D, which will be described later, is in the range of 70 to 6000 μm when focusing on the bottom surface of the protrusion.

In addition, it is preferable that the independent protrusions originate from two adjacent protrusions when the sealing sheet is sandwiched between flat plates, and a pressure of 50 kPa is applied in the thickness direction to compress the protrusions to deform and expand the contact area between the tops of the protrusions and the flat plate. A gap of 20 to 800 μm is secured between the two regions.

The independent protrusions preferably have a ratio (T/D) of the height (T) of the protrusions to the base length (D) of the protrusions of 0.05 to 0.80, more preferably 0.15 to 0.80. When the T/D ratio is less than 0.05, the cushioning properties of the sealing sheet may become insufficient. If the T/D ratio exceeds 0.80, a concentrated load on the top of the protrusions occurs, and cell rupture may occur. The height T of the protrusions is measured as follows. First, the case of having protrusions on one side will be described. Let the surface on the side with the protrusion of the sealing sheet be A surface, and let the surface on the side without a protrusion be B surface. As shown in FIG. 3 , the distance from the vertex of the protrusion on the A surface to the B surface is Tmax, and the distance from the portion without the protrusion on the A surface to the B surface is Tmin. The difference between Tmax and Tmin is the height T of the protrusion. Next, a case where both sides have protrusions will be described. Let one surface of the sealing sheet be A surface, and let the other surface be B surface. As shown in Figure 4, the distance from the vertex of the protrusion on the A surface to the part without protrusion on the B surface is TAmax, and the distance from the vertex of the protrusion on the B surface to the part without protrusion on the A surface is TBmax, The distance from the portion without protrusions on the A surface to the portion without protrusions on the B surface was defined as Tmin. The difference between TAmax and Tmin is the height TA of the protrusions on the A surface, and the difference between TBmax and Tmin is the height TB of the protrusions on the B surface. The length of the base of the protrusion is the outer peripheral diameter D of the protrusion shown in FIG. 5 . Also, when the shape of the bottom of the protrusion is a polygon such as a triangle or hexagon, or an ellipse, the length of the bottom of the protrusion is the diameter of the smallest true circle including the shape of the bottom. The above-mentioned Tmax, Tmin, and D can be measured by observation of the sheet using a stereo microscope.

A preferable height T of the protrusion is 60 to 300 μm as described above. When the height T of the protrusion is 60 μm, the length of the base D of the protrusion is preferably 75 to 1200 μm, more preferably 75 to 400 μm. When the height T of the protrusion is 300 μm, the length of the base D of the protrusion is preferably 375 to 6000 μm, more preferably 375 to 2000 μm.

The number of independent protrusions is preferably 40 to 2300 per 1 cm area of one side of ^two sheets. More preferably, it is 40-1100 pieces. When the number of independent protrusions is less than 40/cm ² , cell breakage and air bubbles may occur. If it exceeds 2300/cm ² , the above-mentioned T/D ratio increases, and cell breakage may occur due to the concentrated load on the top of the protrusions.

The sealing sheet preferably has a heat shrinkage rate of 30% or less in the flow direction of the sheet when left in warm water at 80° C. for 1 minute. More preferably, it is 25% or less. Here, "placed in warm water" means that when the specific gravity of the sealing sheet is small and the sealing sheet floats on the surface of warm water, the sealing sheet is pushed from above without sinking in the warm water, and is in the floating state. down. On the other hand, when the specificity of the sealing sheet is large and the sealing sheet sinks in warm water, the sealing sheet is left in the sinking state without supporting the sealing sheet from below. In addition, "sheet flow direction" is the direction in which the sheet|seat flows in the process in the manufacturing process of a sealing sheet. In a general vacuum lamination process in the manufacture of a solar cell module, the sealing sheet is melted and degassed by evacuating the sheet under no load without applying pressure until the sealing sheet is fully melted. At this time, since the sealing sheet is exposed to a no-load state at a high temperature of about 80° C., shrinkage of the sealing sheet occurs, resulting in cracking and dislocation of cells. The inventors of the present invention have conducted research focusing on the cracking and dislocation of cells, and found that when the process sheet is left for 1 minute in the no-load state reproduced in vacuum lamination, if the heat shrinkage rate in the flow direction of the sheet is 30% or less , the cracking of the unit can be further suppressed. The state reproduced in this vacuum lamination is the state in which the process sheet is placed in warm water at 80°. In addition, the heat shrinkage rate in the direction perpendicular to the flow direction of the sheet is not particularly limited as long as it is slightly smaller than the flow direction, but is preferably 5% or less.

The shape of the independent protrusions is preferably hemispherical, triangular pyramid, quadrangular pyramid, hexagonal pyramid, cone, or other conical shapes, and their tops are flattened into trapezoidal shapes. In addition, these protrusion shapes may exist mixedly. Among them, hemispherical shape and/or quadrangular pyramid shape are preferable. Here, the term "hemispherical and quadrangular pyramidal" means a surface shape in which hemispherical protrusions and quadrangular pyramidal protrusions are mixed. The hemispherical shape is preferable because it is difficult to apply a concentrated load to the solar battery cell when pressing the solar battery cell, and the load can be uniformly distributed. In addition, the quadrangular pyramid shape is also preferable from the viewpoint that unevenness of reflected light is less likely to occur and the surface quality is excellent. In addition, in order to express the characteristics of both the hemispherical shape and the quadrangular pyramid shape, a shape in which the hemispherical shape and the quadrangular pyramid shape are mixed is also preferable. In the case where the hemispherical shape and the quadrangular pyramid shape are mixed, the respective ratios may be arbitrarily determined depending on which feature is more required. Particularly preferred are all hemispherical patterns.

The sealing sheet of the present invention preferably further has protrusions having a height of 1 to 15 μm on the surface having independent protrusions. By having such minute protrusions, the slidability of the sheet is improved and handling becomes easy. In addition, light is scattered by the fine protrusions, and the whiteness of the sheet is improved, so inspection of attached foreign matter and the like becomes easy.

Such minute protrusions can be realized by the manufacturing method of the present invention in which embossing is performed after the annealing step. In the conventional method of annealing by heating after embossing, large protrusions with a height of several 10 μm or more may remain on the sheet even after heat treatment, but fine protrusions with a height of about several μm disappear with heat treatment.

In addition, the height of the minute protrusion is the numerical value measured as follows. The surface of the sheet is photographed at a magnification of 400 using a well-known laser microscope, such as Laser Microscope VK-X100 manufactured by Keyence Co., Ltd., in accordance with JIS B0601 (2001). In the roughness curve of the obtained image, the Rz value at the cutoff value of 0.080 mm was defined as the height of the minute protrusions.

In the present application, the springback stress of the sealing sheet when the surface having the protrusions of the sealing sheet is compressed by 100 μm in the thickness direction is used as an index for evaluating the cushioning properties of the sealing sheet for suppressing cell rupture of the solar battery. As a result of intensive studies on the relationship between the cell breakability of solar cells and the cushioning properties of the sealing sheet, it has been found that the springback stress capable of suppressing cell breakage is preferably 70 kPa or less. In addition, the above-mentioned springback stress is obtained as follows: using a compression test device with a compression displacement of 5 μm or less and a compression load of 100 Pa or less resolution, measure the flat pressurized terminal at a pressurization speed of 0.02 mm/s. The rebound stress (kPa) of the sheet when the surface having the protrusions of the sheet is pressed 100 μm in the thickness direction was obtained. When the sealing sheet has a springback stress of 70 kPa or less, it is possible to suppress cracking of the solar cell by laminating and vacuum laminating so that the surface having the protrusion is in contact with the solar cell. In addition, the shape of the surface of the sealing sheet opposite to the surface having protrusions is not particularly limited, but from the viewpoint of preventing the sealing sheet from sticking at the time of solar cell module manufacture, it is preferable to have a small surface with a height of about 2 to 10 μm. protrusion.

The thickness of the sealing sheet is preferably 50 to 1500 μm. More preferably, it is 100-1000 micrometers, Especially preferably, it is 200-800 micrometers. If it is less than 50 μm, the cushioning properties of the solar cell encapsulating sheet may be insufficient, or a problem may arise from the viewpoint of handleability. Moreover, when it exceeds 1500 micrometers, the fall of productivity and the fall of adhesiveness may become a problem. In addition, the thickness of the sealing sheet is the distance from the apex of the protrusion to the surface on the opposite side to the surface having the protrusion when the protrusion is formed only on one side of the sealing sheet. When protrusions are formed on both surfaces of the sealing sheet, it is the distance from the apex of the protrusions on one surface to the apex of the protrusions on the opposite surface.

In this way, in order to accurately form independent protrusions on the surface of the sealing sheet or to suppress the heat shrinkage rate of the sealing sheet within a specific range, it is preferable to manufacture the sealing sheet by the production method of the present invention.

[Raw materials constituting solar cell sealing sheet]

Next, the resin composition which comprises a sealing sheet is demonstrated. In addition, it is preferable that the resin composition constituting at least the surface portion on the side where the protrusions are formed satisfies the composition and the like of the resin composition described below. Of course, it is more preferable that all the resin compositions constituting the process sheet satisfy the composition and the like of the resin compositions described below.

The resin composition constituting the sealing sheet preferably contains a polyolefin resin. Examples of polyolefin-based resins include polypropylene-based resins such as homopolypropylene, copolymers containing propylene as the main component and other monomers, ethylene-propylene-butene terpolymers, low-density polyethylene, ultra-low-density polyethylene, etc. Polyethylene-based resins such as high-density polyethylene, linear low-density polyethylene, medium-density polyethylene, high-density polyethylene, copolymers of ethylene and other monomers, and polyolefin-based thermoplastic elastomers. Examples of copolymers with other monomers containing ethylene as the main component include ethylene-α-olefin copolymers and ethylene-unsaturated monomer copolymers. Examples of α-olefins include ethylene, propylene, 1-butene, isobutene, 1-pentene, 2-methyl-1-butene, 3-methyl-1-butene, 1-hexene ene, 1-heptane, 1-octene, 1-nonene, 1-decene, etc. Vinyl acetate, acrylic acid, methacrylic acid, methyl acrylate, methyl methacrylate, ethyl acrylate, or vinyl alcohol etc. are mentioned as an unsaturated monomer. In addition, it is one of the preferable forms to carry out a small amount of copolymerization or modification of these polyolefin resins using a silane compound, carboxylic acid, a glycidyl compound, etc. as needed.

Among these polyolefin resins, ethylene-vinyl acetate copolymers, ethylene-methyl methacrylate copolymers, etc. , Resins obtained by modifying low-density polyethylene with ethylenically unsaturated silane compounds, etc. When using an ethylene-vinyl acetate copolymer or an ethylene-methacrylate copolymer, the content of the copolymerization component is preferably in the range of 15 to 40% by mass.

Moreover, it is preferable that the resin composition which comprises a sealing sheet contains an organic peroxide. Any organic peroxide can be used as long as it is an organic peroxide that decomposes at a temperature above 100°C to generate free radicals, as long as the temperature at the time of manufacturing the solar cell sealing sheet is considered, the solar cell module It is sufficient to select the heating lamination temperature at the time, and the storage stability of the crosslinking agent itself. In particular, an organic peroxide having a half-life of 10 hours and a decomposition temperature of 70° C. or higher is preferable. Examples of such organic peroxides include 1,1-di(tert-hexylperoxy)cyclohexane, n-butyl 4,4-di-(tert-butylperoxy)valerate, 2, 5-Dimethyl-2,5-bis(tert-butyl peroxy)hexane, di-tert-butyl peroxide, di-tert-hexyl peroxide, 2,5-dimethyl-2,5- Bis(tert-butylperoxy)hexyne-3, disuccinic acid peroxide, bis(4-tert-butylcyclohexyl)peroxydicarbonate, 1,1,3,3-tetramethylbutylperoxy- 2-ethylhexanoate, tert-hexyl peroxy-2-ethylhexanoate, tert-butyl peroxy-2-ethylhexanoate, tert-hexyl peroxyisopropyl monocarbonate, bis(4- tert-butylcyclohexyl) peroxydicarbonate, tert-butyl peroxy-3,5,5-trimethylhexanoate, tert-butyl peroxylaurate, tert-butyl peroxy-2-ethylhexyl mono Carbonate, tert-butyl peroxy-2-ethylhexanoate, tert-butyl peroxy isobutyrate, tert-butyl peroxyacetate, tert-butyl peroxy isononanoate, tert-amyl peroxy Oxy-2-ethylhexanoate, tert-amyl peroxy-n-octanoate, tert-amyl peroxy isononanoate, tert-amyl peroxy-2-ethylhexyl carbonate, di-tert-amyl peroxy oxide, 1,1-bis(tert-butylperoxy)cyclohexane, ethyl 3,3-bis(tert-butylperoxy)butyrate, 1,1-bis(tert-amylperoxy)cyclohexane Hexane etc. These organic peroxides can be used in combination of 2 or more types. It is preferable that content of these organic peroxides is 0.1-5 mass parts with respect to 100 mass parts of polyolefin resins. More preferably, it is 0.1-3 mass parts, Especially preferably, it is 0.2-2 mass parts. When the content of the organic peroxide is less than 0.1 parts by mass, the polyolefin-based resin may not be crosslinked. Even if it contains more than 5 parts by mass, in addition to the fact that the effect of this content is low, undecomposed organic peroxides may remain in the sealing sheet and cause deterioration over time.

The resin composition constituting the sealing sheet may further contain a crosslinking auxiliary agent, a silane-based coupling agent, a light stabilizer, an ultraviolet absorber, an antioxidant, and the like.

The cross-linking assistant is a polyfunctional monomer with multiple unsaturated bonds in the molecule, which reacts with the active free radical compound generated by the decomposition of organic peroxides, in order to cross-link the polyolefin resin uniformly and efficiently And used. Examples of these crosslinking aids include triallyl isocyanurate, triallyl cyanurate, trimethylolpropane tri(meth)acrylate, pentaerythritol tri(methyl) Acrylates, Tris[(meth)acryloyloxyethyl]isocyanurate, Dimethylolpropane tetra(meth)acrylate, Pentaerythritol tetra(meth)acrylate, Pentaerythritol ethoxy tetra( Meth)acrylate, dipentaerythritol penta(meth)acrylate, dipentaerythritol hexa(meth)acrylate, divinylbenzene, and the like. These crosslinking auxiliary agents may be used alone or in combination of two or more. In addition, in this invention, "(meth)acrylate" means "acrylate or methacrylate".

Among these crosslinking assistants, triallyl isocyanurate and trimethylolpropane tri(meth)acrylate are particularly preferable. The content when these crosslinking assistants are added is preferably 0 to 5 parts by mass with respect to 100 parts by mass of the polyolefin-based resin. More preferably, it is 0.1-3 mass parts, Especially preferably, it is 0.3-3 mass parts. Even if it contains more than 5 parts by mass, the improvement of the effect is small, and it becomes a cost increase factor.

The silane-based coupling agent is preferably used to improve the adhesiveness between the solar cell sealing sheet and various members such as a solar cell, a back sheet, and glass. The content in the case of adding a silane-based coupling agent is preferably in the range of 0.05 to 2 parts by mass with respect to 100 parts by mass of the polyolefin-based resin. If it is less than 0.05 parts by mass, the content effect will be low. Even if it contains more than 2 mass parts, the effect of improving adhesiveness will be low. The silane-based coupling agent is not particularly limited, and examples thereof include at least one type selected from the group having a methacryloxy group, an acryloxy group, an epoxy group, a mercapto group, a urea group, an isocyanate group, an amino group, and a hydroxyl group. Functional alkoxysilane compounds. Specific examples thereof include γ-methacryloxypropylmethyldimethoxysilane, γ-methacryloxypropyltrimethoxysilane, γ-methacryloxypropyl Alkoxysilane compounds containing methacryloxy groups such as methyldiethoxysilane, γ-methacryloxypropyltrimethoxysilane, γ-acryloxypropyltrimethoxysilane Alkoxysilane compounds containing acryloyloxy groups, γ-glycidoxypropyltrimethoxysilane, γ-glycidoxypropyltriethoxysilane, β-(3,4-cyclo Oxycyclohexyl)ethyltrimethoxysilane and other epoxy-containing alkoxysilane compounds, γ-mercaptopropyltrimethoxysilane, γ-mercaptopropyltriethoxysilane and other mercapto-containing alkoxysilanes Compounds, γ-ureidopropyl triethoxysilane, γ-ureidopropyl trimethoxysilane and other alkoxysilane compounds containing urea groups, γ-isocyanatopropyl triethoxysilane, γ-isocyanate Alkoxysilane compounds containing isocyanate groups such as propyltrimethoxysilane, γ-isocyanatopropylmethyldimethoxysilane, γ-(2-aminoethyl)aminopropylmethyldimethoxy Silane, γ-(2-aminoethyl)aminopropyltrimethoxysilane, γ-aminopropyltrimethoxysilane and other amino-containing alkoxysilane compounds, γ-hydroxypropyltrimethoxysilane, γ- Hydroxypropyltriethoxysilane and other hydroxyl-containing alkoxysilane compounds. Among them, a methacryloxy group-containing alkoxysilane compound is preferable from the viewpoint of compatibility with the polyolefin resin, and γ-methacryloxypropyltrimethoxysilane is more preferable.

It is preferable that the resin composition which comprises a sealing sheet further contains an ultraviolet absorber. Ultraviolet absorbers are substances that absorb harmful ultraviolet rays in irradiated light, convert them into harmless heat energy in the molecule, and prevent the excitation of active species that cause photodegradation in polymers. As the ultraviolet absorber, known substances can be used. For example, benzophenone-based, benzotriazole-based, triazine-based, salicylic acid-based, cyanoacrylate-based, and the like can be used. These may be used alone or in combination of two or more.

Examples of benzophenone-based ultraviolet absorbers include 2,2'-dihydroxy-4,4'-bis(hydroxymethyl)benzophenone, 2,2'-dihydroxy-4,4 '-bis(2-hydroxyethyl)benzophenone, 2,2'-dihydroxy-3,3'-dimethoxy-5,5'-bis(hydroxymethyl)benzophenone, 2 ,2'-dihydroxy-3,3'-dimethoxy-5,5'-bis(2-hydroxyethyl)benzophenone, 2,2'-dihydroxy-3,3'-di( Hydroxymethyl)-5,5'-dimethoxybenzophenone, 2,2'-dihydroxy-3,3'-di(2-hydroxyethyl)-5,5'-dimethoxy Benzophenone, 2,2-dihydroxy-4,4-dimethoxybenzophenone, etc.

Examples of benzotriazole-based ultraviolet absorbers include 2-[2'-hydroxy-5'-(hydroxymethyl)phenyl]-2H-benzotriazole, 2-[2'-hydroxy- 5'-(2-hydroxyethyl)phenyl]-2H-benzotriazole, 2-[2'-hydroxy-5'-(3-hydroxypropyl)phenyl]-2H-benzotriazole, 2-[2'-Hydroxy-3'-Methyl-5'-(Hydroxymethyl)phenyl]-2H-Benzotriazole, 2-[2'-Hydroxy-3'-Methyl-5'- (2-Hydroxyethyl)phenyl]-2H-benzotriazole, 2-[2'-hydroxy-3'-methyl-5'-(3-hydroxypropyl)phenyl]-2H-benzo Triazole, 2-[2'-hydroxy-3'-tert-butyl-5'-(hydroxymethyl)phenyl]-2H-benzotriazole, 2-[2'-hydroxy-3'-tert-butyl Base-5'-(2-hydroxyethyl)phenyl]-2H-benzotriazole, 2-[2'-hydroxy-3'-tert-octyl-5'-(hydroxymethyl)phenyl]- 2H-Benzotriazole, 2-[2'-Hydroxy-3'-tert-Octyl-5'-(2-Hydroxyethyl)phenyl]-2H-Benzotriazole, 2-[2'-Hydroxy -3'-tert-octyl-5'-(3-hydroxypropyl)phenyl]-2H-benzotriazole, etc., or 2,2'-methylenebis[6-(2H-benzotriazole -2-yl)-4-(hydroxymethyl)phenol], 2,2'-methylenebis[6-(2H-benzotriazol-2-yl)-4-(2-hydroxyethyl) phenol], 2,2'-methylenebis[6-(2H-benzotriazol-2-yl)-4-(3-hydroxypropyl)phenol], 2,2'-methylenebis[ 6-(2H-benzotriazol-2-yl)-4-(4-hydroxybutyl)phenol], 3,3-{2,2'-bis[6-(2H-benzotriazole-2 -yl)-1-hydroxy-4-(2-hydroxyethyl)phenyl]}propane, 2,2-{2,2'-bis[6-(2H-benzotriazol-2-yl)- 1-Hydroxy-4-(2-hydroxyethyl)phenyl]}butane, 2,2'-oxybis[6-(2H-benzotriazol-2-yl)-4-(2-hydroxy ethyl)phenol], 2,2'-bis[6-(2H-benzotriazol-2-yl)-4-(2-hydroxyethyl)phenol]amine, etc.

Examples of triazine-based ultraviolet absorbers include 2-(2-hydroxy-4-hydroxymethylphenyl)-4,6-diphenyl-s-triazine, 2-(2-hydroxy-4- hydroxymethylphenyl)-4,6-bis(2,4-dimethylphenyl)-s-triazine, 2-[2-hydroxy-4-(2-hydroxyethyl)phenyl]-4, 6-diphenyl-s-triazine, 2-[2-hydroxy-4-(2-hydroxyethyl)phenyl]-4,6-bis(2,4-dimethylphenyl)-s-triazine , 2-[2-hydroxy-4-(2-hydroxyethoxy)phenyl]-4,6-diphenyl-s-triazine, 2-[2-hydroxy-4-(2-hydroxyethoxy )phenyl]-4,6-bis(2,4-dimethylphenyl)-s-triazine, 2-[2-hydroxy-4-(3-hydroxypropoxy)phenyl]-4,6 -Diphenyl-s-triazine, 2-[2-hydroxy-4-(3-hydroxypropoxy)phenyl]-4,6-bis(2,4-dimethylphenyl)-s-triazine , 2-[2-hydroxy-4-(4-hydroxybutyl)phenyl]-4,6-diphenyl-s-triazine, 2-[2-hydroxy-4-(4-hydroxybutyl)benzene Base]-4,6-bis(2,4-dimethylphenyl)-s-triazine, 2-[2-hydroxy-4-(4-hydroxybutoxy)phenyl]-4,6-di Phenyl-s-triazine, 2-[2-hydroxy-4-(4-hydroxybutoxy)phenyl]-4,6-bis(2,4-dimethylphenyl)-s-triazine, 2 -(2-hydroxy-4-hydroxymethylphenyl)-4,6-bis(2-hydroxy-4-methylphenyl)-s-triazine, 2-[2-hydroxy-4-(2-hydroxy Ethyl)phenyl]-4,6-bis(2-hydroxy-4-methylphenyl)-s-triazine, 2-[2-hydroxy-4-(2-hydroxyethoxy)phenyl]- 4,6-bis(2-hydroxy-4-methylphenyl)-s-triazine, 2-[2-hydroxy-4-(3-hydroxypropyl)phenyl]-4,6-bis(2- Hydroxy-4-methylphenyl)-s-triazine, 2-[2-hydroxy-4-(3-hydroxypropoxy)phenyl]-4,6-bis(2-hydroxy-4-methylbenzene base)-s-triazine, etc.

Examples of the salicylic acid-based ultraviolet absorber include phenyl salicylate, p-tert-butylphenyl salicylate, p-octylphenyl salicylate, and the like.

Examples of cyanoacrylate UV absorbers include 2-ethylhexyl-2-cyano-3,3'-diphenylacrylate, ethyl-2-cyano-3,3'-diphenyl acrylates, etc.

Among these ultraviolet absorbers, benzophenone-based ultraviolet absorbers are most preferable from the viewpoint of the ultraviolet absorbing effect and the coloring of the ultraviolet absorber itself.

When adding the above-mentioned ultraviolet absorber, it is preferably 0.05 to 3 parts by mass with respect to 100 parts by mass of the polyolefin-based resin. More preferably, it is 0.05-2.0 mass parts. When the content is less than 0.05 parts by mass, the effect of containing is low, and when it exceeds 3 parts by mass, coloring tends to occur.

The resin composition constituting the sealing sheet preferably further contains a light stabilizer. A light stabilizer is a substance that supplements free radical species harmful to polymers and does not generate new free radicals. As the light stabilizer, a hindered amine light stabilizer is preferably used.

As hindered amine light stabilizers, bis(2,2,6,6-tetramethyl-1(octyloxy)-4-piperidinyl) sebacate, A mixture of 70% by mass of the reaction product of methyl ethyl hydroperoxide and octane and 30% by mass of polypropylene, bis(1,2,2,6,6-pentamethyl-4-piperidinyl) [[3,5-bis(1,1-dimethylethyl)-4-hydroxyphenyl]methyl]butylmalonate, bis(1,2,2,6,6-pentamethyl -4-piperidinyl) sebacate and methyl-1,2,2,6,6-pentamethyl-4-piperidinyl sebacate mixture, bis(2,2,6,6- Tetramethyl-4-piperidinyl) sebacate, tetrakis(2,2,6,6-tetramethyl-4-piperidinyl)-1,2,3,4-butane tetracarboxylate , Four (1,2,2,6,6-pentamethyl-4-piperidinyl)-1,2,3,4-butane tetracarboxylate, 2,2,6,6-tetramethyl -4-piperidinyl-1,2,3,4-butane tetracarboxylate and tridecyl-1,2,3,4-butane tetracarboxylate mixture, 1,2,2, Mixture of 6,6-pentamethyl-4-piperidinyl-1,2,3,4-butane tetracarboxylate and tridecyl-1,2,3,4-butane tetracarboxylate , poly[{6-(1,1,3,3-tetramethylbutyl)amino-1,3,5-triazine-2,4-diyl}{(2,2,6,6-tetramethylbutyl) Methyl-4-piperidinyl)imino}hexamethylene{(2,2,6,6-tetramethyl-4-piperidinyl)imino}], dimethyl succinate and 4-hydroxy -2,2,6,6-Tetramethyl-1-piperidine ethanol polymer, N,N',N'',N'''-tetrakis-(4,6-bis-(butyl-( N-methyl-2,2,6,6-tetramethylpiperidin-4-yl)amino)-triazin-2-yl)-4,7-diazadecane-1,10-diamine Mixture with the above polymer of dimethyl succinate and 4-hydroxy-2,2,6,6-tetramethyl-1-piperidineethanol, dibutylamine·1,3,5-triazine·N ,N'-bis(2,2,6,6-tetramethyl-4-piperidinyl-1,6-hexanediamine and N-(2,2,6,6-tetramethyl-4-piperidinyl Polycondensate of pyridyl)butylamine, etc. The above-mentioned hindered amine light stabilizers may be used alone or in combination of two or more.

Among them, as hindered amine light stabilizers, bis(1,2,2,6,6-pentamethyl-4-piperidinyl) sebacate and methyl-1,2,2,6, Mixture of 6-pentamethyl-4-piperidinyl sebacate, and methyl-4-piperidinyl sebacate, bis(2,2,6,6-tetramethyl-4-piperidine base) sebacate. In addition, as the hindered amine light stabilizer, it is preferable to use a hindered amine light stabilizer having a melting point of 60° C. or higher.

The content in the case of adding a hindered amine light stabilizer is preferably 0.05 to 3.0 parts by mass relative to 100 parts by mass of the polyolefin resin. More preferably, it is 0.05-1.0 mass part. If the content is less than 0.05 parts by mass, the stabilizing effect will be insufficient, and even if it is contained in excess of 3.0 parts by mass, it will cause coloring and cost increases.

In addition, known additives such as antioxidants, flame retardants, flame retardant aids, plasticizers, lubricants, colorants, and the like may be contained as needed within the range that does not impair the effects of the present invention.

[solar battery module]

The solar cell module is composed of a light-receiving surface protector, a back protector, and a layer arranged between the light-receiving surface protectant and the back protector and sealed with solar cells by a sealing sheet. As the sealing sheet used here, the sealing sheet obtained by the manufacturing method of this invention can be used, and the above-mentioned sealing sheet which has independent protrusion on the surface can also be used.

The sealing sheet obtained by the production method of the present invention has a small heat shrinkage when the materials having the above-mentioned constitution are laminated and integrated. Therefore, the residual stress during molding between the solar cell and the sealing sheet, between the light-receiving surface protector and the sealing sheet, and between the back protector and the sealing sheet is small, and the solar cell has excellent long-term durability. module.

In addition, the above-mentioned sealing sheet having independent protrusions on the surface can disperse the pressing force on the solar cell when the materials of the above structure are laminated and integrated, so the residual stress between the solar cell and the sealing sheet can be reduced. In addition, air bubbles do not remain in the seal. Therefore, it becomes a solar cell module excellent in long-term durability.

Example

The measurement methods used in this example are shown below. Unless otherwise specified, the number of measurement n is 5, and the average value is adopted.

(1) Thickness of sheet

About the molded sealing sheet, the thickness of arbitrary 20 points was measured in the width direction, and the average thickness was calculated|required. As a measuring instrument, a thickness gauge (model 547-301) manufactured by Mitsutoyo Co., Ltd. was used. Regarding the thickness of the sealing sheet, when the protrusions are formed only on one side of the sealing sheet, the distance from the apex of the protrusions to the surface on the opposite side to the surface having the protrusions is measured. When protrusions are formed on both surfaces of the sealing sheet, the distance from the apex of the protrusion on one surface to the apex of the protrusion on the opposite surface is measured.

(2)Protrusion height

The sealing sheet is cut in a direction (width direction) perpendicular to the moving direction of the sheet during production (hereinafter, simply referred to as the MD direction) so as to pass through the top of the protrusion. The thickness direction cross section of the cut|disconnected sealing sheet was observed with the stereomicroscope over the entire width of a sheet|seat.

When the sealing sheet has a protrusion on one surface, let the surface of the sealing sheet on the side with the protrusion be the A surface, and let the surface on the side without the protrusion be the B surface. As shown in FIG. 3 , the distance from the vertex of the protrusion on the A surface to the B surface is Tmax, and the distance from the portion without the protrusion on the A surface to the B surface is Tmin. Then, the height T of the protrusion is calculated from the formula (i).

·T(μm)＝Tmax－Tmin···(i)

When both surfaces of a sealing sheet have a protrusion, let one surface of a sealing sheet be A surface, and let the other surface be B surface. As shown in Figure 4, the distance from the vertex of the protrusion on the A surface to the part without protrusion on the B surface is TAmax, and the distance from the vertex of the protrusion on the B surface to the part without protrusion on the A surface is TBmax, The distance from the portion without protrusions on the A surface to the portion without protrusions on the B surface was defined as Tmin. Then, the height TA of the protrusions on the A surface is calculated from the formula (ii), and the height TB of the protrusions on the B side is calculated from the formula (iii).

·TA(μm)＝TAmax－Tmin···(ii)

· TB (μm) = TBmax - Tmin · · · (iii).

(3) Pattern depth of embossing roller

The surface of the embossing roll was measured under the measurement conditions of a reference length of 20 mm, a load of 0.75 mN, and a measurement speed of 0.3 mm/s in accordance with JIS B0601 (2001). The measurement was performed using a small-sized surface roughness measuring instrument SJ401 manufactured by Mitsutoyo Co., Ltd., using a diamond stylus with a cone of 60° and a tip curvature radius of 2 μm. This measured value was made into the pattern depth Pz value (micrometer) of an embossing roll.

(4) Embossing transfer rate

Calculated by dividing the protrusion height T (μm) (or protrusion height TA (μm) or protrusion height TB (μm)) measured in (2) above by the pattern depth Pz of the embossing roll measured in (3) above The value of is set to the embossing transfer rate.

· Embossing transfer rate (%)=T/Pz×100.

(5) heating shrinkage

A test piece having a plane square shape with a side of 120 mm was cut out from the sealing sheet. On this test piece, two parallel straight lines (5 cm) in the TD direction were drawn at an interval of 100 mm at the central part in the TD direction during manufacture. Then, marks are made at the positions (5 positions) that divide each straight line into 6 equal parts.

Next, the test piece was left to stand in warm water heated to 80° C. for 60 seconds. When the specific gravity of the sealing sheet is small and the sealing sheet floats on the warm water surface, it is left in the floating state. When the specificity of the sealing sheet is large and the sealing sheet sinks in warm water, it is left in the sinking state. After 60 seconds had elapsed, the test piece was taken out from the warm water, immersed in 20° C. normal temperature water for 10 seconds and cooled, and then the moisture on the surface of the piece was removed.

Use the vernier to measure the interval A (mm) between each mark at 5 places drawn on a straight line drawn on the test piece and the opposing marks made on another straight line, calculate the heat shrinkage rate based on the following formula, and obtain 5 average value at .

?Heat shrinkage (%)=(100－A)/100×100.

(6) Melt flow rate of the resin composition constituting the sealing sheet

For the resin composition, in accordance with JIS K7210 (1999) "Plastics - Thermoplastics Melt Mass Flow Rate (MFR) and Melt Volume Flow Rate (MVR) Test Method", at a temperature of 190 ° C and a load of 2.16 kg test conditions Next measure.

(7) Length of the bottom edge of the protrusion (D)

The surface having the protrusions of the sheet was observed with a stereomicroscope, and the base length (D) was measured. When the shape of the bottom surface of the protrusion is a polygon such as a triangle or a hexagon, or an ellipse, the diameter of the smallest true circle including the above-mentioned shape is measured.

(8) Unit rupture

Two test pieces having a plane square shape with a side of 180 mm were cut out from the sealing sheet. Inner wires (thickness 280 μm, width 2 mm) were soldered to polycrystalline solar cells (3 bus bars, size 156 mm square, thickness 200 μm) to produce solar cells with interconnections. A glass plate (180 mm square, 3 mm thick) and a polyester solar battery back sheet (180 mm square, 240 μm thick) were prepared. A sealing sheet, a solar cell, a sealing sheet, and a back sheet are sequentially stacked on a glass plate. At this time, the sealing sheet is laminated so that the surface having the protrusions is in contact with the solar cell. This laminate was subjected to vacuum lamination at a temperature of 145° C., evacuated for 30 seconds, pressed for 1 minute, and kept under pressure for 10 minutes to produce a solar cell module. For the obtained solar cell module, an emission image was captured by a solar cell EL image inspection device, and the length (mm) of the total cracks in the cell rupture was measured. This test was repeated 3 times, and the average value of the total crack length was calculated|required.

(9) Number of bubbles

The number of bubbles in the solar cell module produced in (8) above was counted visually. Find the average of 3 trials.

(10) Rebound stress

A test piece having a plane square shape with a side of 120 mm was cut out from the sealing sheet. Next, using a compression tester KES FB-3 manufactured by Kato-Tec Co., Ltd., pressurize the sealing sheet at a speed of 20 μm/sec through a flat pressurized terminal with a diameter of 16 mm from the surface with protrusions of the test piece, and measure the pressurization in the thickness direction. Rebound stress (kPa) of the sheet at 100 μm. This test was repeated three times, and the average value of the springback stress was obtained.

(Example 1)

According to the manufacturing method shown in Figure 1, the solar cell sealing sheet is made

Process (a): film forming process

A twin-screw extruder was used as the extruder 11, and 100 parts by mass of EVA (vinyl acetate content: 28% by mass, melt flow rate: 15 g/10 minutes, melting point: 71° C.), tert-butyl peroxide- 0.7 parts by mass of 2-ethylhexyl monocarbonate (1-hour half-life temperature: 119°C), 0.3 parts by mass of triallyl isocyanurate, 0.2 parts by mass of γ-methacryloxypropyltrimethoxysilane 0.3 parts by mass of 2-hydroxy-4-methoxybenzophenone, 0.1 parts by mass of bis(1,2,2,6,6-pentamethyl-4-piperidinyl) sebacate The composition was supplied to the extruder 11 set at 80° C. and melt-kneaded. The kneaded resin composition was extruded from the T-die 12 connected to the extruder 11 and maintained at 105°C. In addition, the lip width of the T-shaped die used was 1300 mm, and the lip gap was 0.8 mm.

The resin composition extruded in this way was cooled and solidified by the buff roll 13a, 13b, 13c held at 20 degreeC, and it was made into a sheet form. In addition, the temperature of the process sheet at the time of discharging from the T-die was 107°C. In addition, the process sheet at this time had a width of 1150 mm, a thickness of 450 μm, and a conveying speed of 10 m/min.

Process (b): Annealing process

Next, annealing treatment was performed under the conditions described in Table 1.

For heating, a ceramic heater 16 is used, and the conveying roller 17 is a conveying roller in which a metal roller having a diameter of 150 mm and coated with "Teflon (registered trademark)" is used at intervals such that the center-to-center distance of the rollers is 200 mm. . As the annealing furnace 15, the annealing furnace which wound the heat insulating material around the case made of SUS was used. In addition, hot air was blown in at a wind speed of 1 m/sec from the lower portion of the entrance and the lower portion of the exit of the annealing furnace 15 .

Step (c): Embossing process

Under the conditions described in Table 1, embossing was performed continuously with the annealing treatment.

The embossing was carried out by passing the process sheet conveyed from the annealing furnace between the embossing roll 20 with a pattern depth of 120 μm and the embossing counter roll 19 wound with silicone rubber having a thickness of 10 mm and a hardness of 75°.

The heat shrinkage rate and embossing transfer rate of the obtained solar cell sealing sheet were evaluated. The results are shown in Table 1. As shown in Table 1, a solar cell sealing sheet in which the heat shrinkage rate was very small and the embossed pattern was clearly transferred was obtained.

(Example 2)

A sealing sheet was produced in the same manner as in Example 1, except that the temperature of the hot air in the step (b) was 87°C, the heater temperature was 320°C, and the residence time in the furnace was 29 seconds. material. Since the surface temperature of the process sheet was lowered, the heating shrinkage rate was slightly increased, and the embossing transfer rate was slightly lower, but similar to Example 1, the heating shrinkage rate was very small, and the embossing pattern was clearly transferred. solar cell sealing sheet.

(Example 3)

The temperature of the hot air in the process (b) is set to 80°C, the heater temperature is set to 300°C, the residence time in the furnace is set to 30 seconds, and the line pressure is set to 450N/cm, and the process is carried out by and The sealing sheet was made in the same way as Example 1. Since the surface temperature of the process sheet was further lowered, the heating shrinkage ratio increased slightly, and the embossing transfer ratio decreased slightly, but similar to Example 1, the heating shrinkage ratio was very small, and the embossing was clearly transferred. Patterned solar cell encapsulation sheet.

(Example 4)

The sealing sheet was produced by the method similar to Example 3 except having made the linear pressure in a process (c) into 200 N/cm. Although the embossing transfer rate became slightly low, the solar cell sealing sheet in which the embossing pattern was clearly transferred was obtained similarly to Example 3.

(Example 5)

The hot air temperature in the process (b) is set to 110°C, the residence time in the furnace is set to 27 seconds, and the linear pressure in the process (c) is set to 200N/cm, except that, by the same method as in Example 1 method to make slices. Since the surface temperature of the process sheet rises, a solar cell sealing sheet having a very small heat shrinkage rate and a clear embossing transfer rate is obtained.

(Example 6)

A sealing sheet was produced in the same manner as in Example 5 except that the angle of attachment to the embossing roll in the process (c) was 45°. Although the embossing transfer rate was slightly reduced due to the small hug angle, it was a sheet with a good appearance.

(Example 7)

The conveying speed of the process sheet in the process (b) is set to 7m/min, the hot air temperature is set to 110°C, the heater temperature is set to 300°C, the residence time in the furnace is set to 39 seconds, and the process (c) The sealing sheet was produced by the method similar to Example 1 except having set the linear pressure in 120 N/cm. The heating time of the process sheet becomes longer and the surface temperature becomes higher, so the heat shrinkage rate is greatly reduced, and the embossed shape sheet can be produced clearly even when the line pressure is low.

(Comparative examples 1 to 5)

Except having applied the conditions shown in Table 2, the solar cell sealing sheet was produced by the method similar to Example 1.

(Comparative examples 6 and 7)

According to the conventional manufacturing method shown in FIG. 2, embossing is performed immediately after extrusion from a T-die, and an annealing treatment is performed thereafter. The annealing treatment device was the same as in Example 1, and the embossing roll 13b' immediately behind the T-die used a roll with a pattern depth of 120 µm.

[Table 1]

[Table 2]

(result)

As shown in Table 1, the solar cell sealing sheets produced in Examples 1 to 7 had a small heating shrinkage rate, and a high embossing transfer rate, and the embossed shape was clearly transferred.

Using these solar cell sealing sheets, a solar cell module was produced by a conventionally known method. As a result, when the module was produced, there were no defects such as cell displacement, cell cracking, or air bubble mixing.

In Comparative Example 1, since the temperature during the annealing treatment and the sheet temperature at the entrance of the embossing roll 20 were both low, the heat shrinkage rate was also large and the embossing transfer rate was also low. In Comparative Example 3, since the distance between the exit of the annealing furnace and the entrance of the embossing roll was enlarged, the temperature of the sheet decreased, and the embossing transfer rate decreased. In Comparative Example 4, since the sheet surface temperature in the annealing furnace was low, the heat shrinkage rate could not be sufficiently reduced.

In Comparative Example 2, the process sheet was wound on an embossing roll, and a sample could not be obtained.

In Comparative Example 5, since the annealing treatment time was short, the heat shrinkage of the solar cell sealing sheet could not be sufficiently reduced.

In Comparative Examples 6 and 7, the embossed shape was not clear because the embossed shape was imparted by a polishing roll, but the embossed shape collapsed if the heat shrinkage was reduced, and the heat shrinkage could not be reduced if the embossed shape was maintained.

(Embodiment 8)

Process (a): film forming process

Containing 100 parts by mass of EVA (vinyl acetate content: 28% by mass, melt flow rate: 15 g/10 minutes (190°C), melting point: 71°C), tert-butylperoxy-2-ethylhexyl monocarbonate (1-hour half-life temperature: 119°C) 0.7 parts by mass, 0.3 parts by mass of triallyl isocyanurate, 0.2 parts by mass of γ-methacryloxypropyltrimethoxysilane, 2-hydroxy-4- A resin composition of 0.3 parts by mass of methoxybenzophenone and 0.1 parts by mass of bis(1,2,2,6,6-pentamethyl-4-piperidinyl) sebacate was supplied to 80 ℃ twin-screw extruder and melt kneading. The kneaded resin composition was extruded from a T-die connected to a twin-screw extruder maintained at 105°C. In addition, the lip width of the T-shaped die head is 1300mm, and the lip gap is 0.8mm.

The EVA sheet was cooled and solidified by passing through a polishing roll kept at 20°C. In addition, the sheet temperature at the time when the EVA sheet was discharged from the T-die was 107°C. In addition, the sheet width at this time was 1150 mm, the sheet thickness was 450 μm, and the sheet conveying speed was 10 m/min. Next, annealing treatment and embossing are successively performed.

Process (b): Annealing process

The annealing treatment was carried out by installing a ceramic heater with a surface temperature of 350° C., and installing a metal with a diameter of 150 mm and coated with “Teflon (registered trademark)” on the surface at intervals such that the center-to-center distance of the rollers was 250 mm. The roller passes through an annealing furnace in which a heat insulating material is wound around a SUS casing. In addition, hot air was blown in at a wind speed of 1 m/sec from the lower inlet and outlet of the furnace.

Step (c): Embossing process

The embossing process was performed as follows: the sheet taken out of the annealing furnace was wound with a hardness 75 with a thickness of 10 mm on an embossing roll having a pattern depth of 180 μm, a diameter of 460 μm, and a hemispherical concave engraved pattern at 450 pieces/cm ² . ° Pass between opposing rolls of silicone rubber.

In addition, the details of the above-mentioned production conditions are as follows.

Sheet surface temperature at the entrance of the annealing furnace: 23°C

Hot air temperature: 93°C

Maximum temperature of sheet surface in annealing furnace: 90°C

Sheet surface temperature at the exit of the annealing furnace: 90°C

Sheet residence time in the annealing furnace: 28 seconds

Sheet speed at exit 15 of the annealing furnace: 9.6m/min

Sheet surface temperature at the entrance of the embossing roller: 78°C

Embossing roller temperature: 15°C

Line pressure of embossing roller: 350N/cm

The angle of attachment to the embossing roller: 120°.

The heat shrinkage rate and springback stress of the obtained sealing sheet, the cell rupture property at the time of module manufacture, and the number of bubbles were evaluated. The results are shown in Table 3. As shown in Table 3, the heat shrinkage rate of the sheet was small, and the sealing sheet had a small number of cell cracks and air bubbles during module production.

(Example 9)

The embossing roll in the step (c) was changed to 450 pieces/ ^cm2 with a pattern depth of 120 μm, a diameter of 460 μm and a hemispherical concave engraving pattern, except that, by the same method as in Example 8 method to make a sealing sheet.

As shown in Table 3, the obtained sealing sheet had a small heat shrinkage rate of the sheet, and had a small number of cell ruptures and bubbles during module production.

(Example 10)

The embossing roll in the step (c) was changed to 450 pieces/cm ² having a pattern depth of 300 μm, a diameter of 460 μm and a hemispherical concave engraved pattern embossing roll, except that, by the same method as in Example 8 method to make a sealing sheet.

As shown in Table 3, the obtained sealing sheet had a small heat shrinkage rate of the sheet, and had a small number of cell ruptures and bubbles during module production.

(Example 11)

The embossing roll in the step (c) was changed to 980 pieces/cm ² having a pattern depth of 300 μm, a diameter of 330 μm and a concave embossing pattern of a hemispherical shape, except that, by the same method as in Example 8 method to make a sealing sheet.

As shown in Table 3, the obtained sealing sheet had a small heat shrinkage rate of the sheet, and had a small number of cell ruptures and bubbles during module production.

(Example 12)

The embossing roll in the process (c) is changed to 840 pieces/cm ² with a pattern depth of 180 μm, an embossing roll with an outer peripheral diameter of 460 μm and a concave engraved pattern in the shape of a quadrangular pyramid. The same method is used to make the sealing sheet.

As shown in Table 3, the obtained sealing sheet was a sealing sheet with a small heat shrinkage rate of the sheet and few air bubbles, although some cell cracks occurred during module manufacture.

(Example 13)

The sealing sheet was produced by the method similar to Example 8 except having heated the sheet|seat surface temperature to 90 degreeC with the infrared heater, and embossed without performing an annealing process.

As shown in Table 3, the obtained sealing sheet had a large thermal shrinkage rate of the sheet and some cell cracks during module production occurred, but it was a sealing sheet with few air bubbles.

(Example 14)

The sealing sheet was produced by the method similar to Example 8 except having changed EVA resin into the EVA resin of melt flow rate 10g/10min. As shown in Table 3, the obtained sealing sheet was a sealing sheet with a small heat shrinkage rate of the sheet and few air bubbles, although some cell cracks occurred during module manufacture.

(Example 15)

The embossing roll in the step (c) was changed to 45 pieces/cm ² with a pattern depth of 180 μm, an embossing roll with an outer peripheral diameter of 2000 μm and a concave engraved pattern in the shape of a quadrangular pyramid. The same method is used to make the sealing sheet.

As shown in Table 3, the obtained sealing sheet was a sealing sheet with few air bubbles, although the heat shrinkage rate of the sheet was small, and cell cracking at the time of module production occurred to some extent.

(reference example 1)

Except not embossing, the sealing sheet which performed up to annealing process was produced by the method similar to Example 8, and it used for evaluation.

As shown in Table 4, the obtained sealing sheet had a small heat shrinkage rate, but it was a sealing sheet in which cells were broken during module production and a large number of air bubbles were generated.

(reference example 2)

In addition to changing the embossing roll in the step (c) to an embossing roll with a pattern depth of 180 μm and an engraving pattern having continuous semicircular grooves (groove width 460 μm) in the direction of rotation of the roll, the same method as in Example 8 The same method is used to make a sealing sheet.

As shown in Table 4, the obtained sealing sheet was a sealing sheet with many bubbles, although the heat shrinkage rate of the sheet was small and there were few cell cracks during module production.

(reference example 3)

The embossing roll in the step (c) was changed to 450 pieces/cm ² with a pattern depth of 50 μm, a diameter of 460 μm and a hemispherical concave engraving pattern, except that, by the same method as in Example 8 method to make a sealing sheet.

As shown in Table 4, the obtained sealing sheet had a small heat shrinkage rate, but had cell rupture and many air bubbles during module production.

(reference example 4)

The embossing roll in the step (c) was changed to 4500 pieces/cm ² with a pattern depth of 180 μm, a diameter of 150 μm and a hemispherical concave engraved pattern embossing roll, except that, by the same method as in Example 8 method to make a sealing sheet.

As shown in Table 4, the obtained sealing sheet had a small heat shrinkage rate and few air bubbles, but had many cell cracks during module production.

(reference example 5)

The embossing roll in the step (c) was changed to 7 embossing rolls/ ^cm2 having a pattern depth of 180 μm, a diameter of 3800 μm and a hemispherical concave engraving pattern, except that, by the same method as in Example 8 method to make a sealing sheet.

As shown in Table 4, the obtained sealing sheet had a small heat shrinkage rate, but had many cell cracks and air bubbles during module production.

[table 3]

[Table 4]

industry availability

This invention can be used very suitably for the manufacturing method of a solar cell sealing sheet. In particular, since heat shrinkage is reduced and a clear embossed pattern is provided, it is possible to prevent positional displacement of cells during module manufacturing and air bubbles in the module, etc., and it is possible to remarkably improve the productivity of the module.

Explanation of symbols

1 process piece

11 twin screw extruder

12 die heads

13a Polishing roller (without engraving on the surface)

13b Polishing roller (no engraving on the surface)

13b’ embossing roller (with engraving on the surface)

13c Polishing roller (without engraving on the surface)

14 rolls

15 Annealing furnace

16 heater

17 conveyor roller

18 piece take-out roller

19 embossing counter roll

20 embossing rollers

21 cooling roll

31 gear pump

32 piece conveying direction

33 Non-contact infrared thermometer.

Claims (11)

1. the manufacture method of a solar cell sealing sheet material, carry out following operation (a), operation (b) and operation (c) successively,

Operation (a): will be by heating melting resin combination be shaped to sheet, then carry out cooling, thereby obtain the operation of operation sheet;

Operation (b): at least one surface heating of the operation sheet that will be obtained by described operation (a) 22～55 seconds adds the operation of the temperature more than the fusing point of hankering making this surperficial temperature reach the resin combination that forms this surface portion at this;

Operation (c): the temperature on the surface of the operation sheet that has made to be heated in described operation (b) is (fusing point of the resin combination of described formation surface portion-10 ℃)～(fusing point of the resin combination of described formation surface portion+20 ℃), then to this surface, press dandy roll, form the operation of embossing shape on this surface.

2. the manufacture method of solar cell sealing sheet material according to claim 1, in described operation (c), when pressing described operation sheet surperficial with described dandy roll, making the linear pressure that this surface is subject to is 150～500N/cm.

3. the manufacture method of solar cell sealing sheet material according to claim 1 and 2, in described operation (c), when pressing described operation sheet surperficial with described dandy roll, make the surface temperature of this dandy roll for below (fusing point of the resin combination of described formation surface portion-20 ℃).

4. according to the manufacture method of the described solar cell sealing sheet material of any one of claim 1～3, in described operation (a), use single screw extrusion machine or double screw extruder will be by described heating melting resin combination extrude and be shaped to sheet from die head.

5. according to the manufacture method of the described solar cell sealing sheet material of any one of claim 1～4, the resin combination of described formation surface portion comprises polyolefin-based resins and organic peroxide.

6. a solar cell sealing sheet material, be the solar cell sealing sheet material obtained by the described manufacture method of any one of claim 1～5,

The resin combination of described formation surface portion comprises polyolefin-based resins,

Be formed with the individual bumps of every square centimeter, surface with 40～2300 height 60～300 μ m of described embossing shape, and the height T of this individual bumps and the ratio T/D of base length D are 0.05～0.80.

7. solar cell sealing sheet material according to claim 6, when described solar cell sealing sheet material is placed to 1 minute in the warm water of 80 ℃, the flow heat shrink rate of direction of the sheet of sealing sheet material is below 30%.

8. according to the described solar cell sealing sheet material of claim 6 or 7, described individual bumps be shaped as hemispherical and/or quadrangular pyramid shape.

9. according to the described solar cell sealing sheet material of any one of claim 6～8, when the face with described projection by described solar cell sealing sheet material compresses 100 μ m along the thickness direction of sealing sheet material, the resilience stress of sheet is below 70kPa.

10. according to the described solar cell sealing sheet material of any one of claim 6～9, bossed of the tool of described solar cell sealing sheet material further has the projection of height 1～15 μ m.

11. a solar module, it is configured to: the layer that contains sensitive surface guard member, back-protective part and be configured between this sensitive surface guard member and back-protective part and be sealed with by the described solar cell sealing sheet material of any one of claim 6～10 solar battery cell.

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